Process for deoxidizing hydrocarbons



Feb. 13, 1940. w. B. PLUMMER ET AL PROCESS FOR DEOXIDING HYDROCARBONS Filed Nov. 27, 1937 Deoxidizea Gas or Liquid CON CEN 7' R4750 serum/6 DRUM Gas or Lia/b confa/ning 0 Wasfe Mafer/a/ lnvenfor's mlllamfi lummer' Y dzwf 7 4 ATTORNEY Patented Feb. 13, 1940 UNITED STATES PROCESS FOR DEOXI'DIZING- HYDROCARBONS WilliamB. Plummer, Chicago, and Maurice H.

Arveson, Flossmoor, Ill., assignors to Standard Oil Company, Chicago, 111., a corporation of Indiana Application November 2'1, 1937, Serial No. 176,902

6 Claims.

5 In many processes involving .the treatment of fluid hydrocarbons, the presence of oxygen in the hydrocarbons being treated produces undesirable results. In the cracking of hydrocarbon oils, for example, oxygen in the feed stock causes increased corrosion of furnace tubes and heat exchangers, and in the recovery of low-boiling liquids from hydrocarbon gases by absorption in an absorberyoil, oxygen in the gas feed renders "zthelrichwoil corrosive to heat exchangers, pipe lines,etc. Often these and other detrimental results are produced by a very small amount of oxygen, which has heretofore been difficult to remove at low cost. By means of this invention oxygen, particularly in relatively small amounts, may be easilyand inexpensively removed from gaseous or liquid hydrocarbons.

' It is an object of this invention to provide an improved process for deoxidizing hydrocarbons.

Another object is to provide a process for deoxidizing hydrocarbons by contacting the same with an acidic aqueous solution in the presence of metallic iron.

Further objects will be apparent from' the following detailed description.

The invention comprises broadly the contacting of fluid hydrocarbons containing oxygen, particularly in small amounts, with a dilute acidic aqueous solution in the presence of metallic iron. The fluid hydrocarbon may be either a gas, such as natural gas or gas produced in a cracking operation, or a liquid hydrocarbon such as cracking still charging stock, absorber oil, lubricating oil, gasoline, etc., and it may contain other impurities such as hydrogen sulfide. Any suitable acid may be used, but sulfuric and hydrochloric acids are preferred because of their low cost. The effective acid concentration employed is preferably in the range 0.001 to 0.1 normal, depending'upon the temperature and pressure employed and the concentration of oxygen and hydrogen sulfide in the hydrocarbons being deoxidized. If hydrogen sulfide is present the concentration should be sumcient to prevent the precipitation of iron sulfides from the solution, and in general will be higher at increased pressures. Any suitable temperature and pressure may be used, the conditions chosen being such that no more than a very small amount of water is lost from the solution by vaporization.

Solutions of salts having an acid reaction within the range of 0.001 to 0.1 normal effective acid concentration (hydrogen ion concentration) 5 may also be used, such salts being exemplified by the acid sulfates, acid phosphates, and the like.

The principal reaction involved in theremoval of oxygen from hydrocarbon fluids according to the invention is believed to be the direct oxidation or rusting of the iron with the formation .of ferric oxide. The acid solution serves the dual function of. providing suitable conditions for the reaction, and preventing precipitation of iron sulfides from the solution if hydrogen sulfide is present. It is apparent, however, that some iron will dissolve directly in the acid with the formation of the ferrous salt, and that some oxygen will therefore be used in oxidizing this salt to the ferric state.

Referring now to the drawing which shows diagrammatically one type of apparatus suitable for practicing the invention, the hydrocarbon gas or liquid from which oxygen is to beremoved is introduced through line l0 and spray coil ll into the bottom of deoxidizing tower l2, which is filled with iron fragments I3, preferably junk iron having a size of about onefourth inch to one inch, supported on a perforated plate H. The iron fragments act to insure intimate contact between the fluid and the solution as well as enter into the reaction. The hydrocarbon" fluid passes up tower I 2 countercurrent to a stream of dilute acidic solution, preferably having an effective acid concentration of 0.001 to 0.1 normal as herein above described, which is supplied to the upper portion of tower I! through line l5 and spray coil IS. The oxygen in the hydrocarbon fluid is removed during this treatment, and the purified gas or liquid is removed from the top of tower I! through line I! for further processing or to storage.

Y The acid solution in the bottom of tower I 2, which contains some ferric salts in solution and may also contain some ferric oxide in suspension, is withdrawn therefrom by means of line I! and introduced into settling drum l 9, in which the suspended matter, if any, is allowed to settle out. The clear solution from the top of settling drum I9 is returned to the top of tower l2 through valve 20 by means of line 2|, pump 22 and lines I! and lb. The solid material in the bottom of settling drum la is periodically removed together with some solution through valve 24 and line 25.

It may be necessary .to add acid to the solution from time to time in order to maintain its concentration, and this may be done by withdrawing concentrated acid from storage tank 26 by means of line 21 and pump 28, and introducing it into line I5 through line 29, valve 30, line 3! and valve 32. Water may be introduced into the system periodically to make up the required volume through line 33, pump 34, line 35, valve 36, line 3| and valve 32.

Although the process may be operated continuously for long periods of time, the solution eventually will become so saturated with salts and other material that it is discarded through valve 24 and line 25. The system is then flushed out with water from line 33 by means of pump 34, valves 20 and 30 being kept'closed, and fresh acid is added through pump 28, line 29 and valve 30 until the proper concentration is obtained. The iron fragments in tower 12 will also be gradually used up and fresh fragments will therefore be added in the upper portion of tower l2 by well known means not shown.

The invention is not limited to the use of a countercurrent treater, but other types of treating equipment such as concurrent mixer-settler systems may be used. The apparatus, as will be apparent to one skilled in the art, may be modified in numerous ways, and should be constructed of materials that resist the action of acids in the concentrations used.

Although we have described a specific embodiment of our invention and certain theories regarding it, we do not desire to be limited thereto, but only by the following claims, which should be construed as broadly as the prior art will permit.

We claim:

1. The process of removing small amounts of oxygen from a hydrocarbon fluid containing the same, comprising contacting said fluid with a dilute acidic aqueous solution having an hydrogen ion concentration of about 0.001 to 0.1 normal in the presence of metallic iron.

2- The process of removing small amounts of oxygen from a hydrocarbon fluid containing the same, comprising contacting said fluid with a dilute acidic aqueous solution having an hydrogen ion concentration of about 0.001 to 0.1 normal in the presence of a contact mass comprising iron fragments.

3. The process of removing small amounts of oxygen from a hydrocarbon fluid containing the same, comprising contacting said fluid with a dilute acidic aqueous solution having an hydrogen ion concentration of about 0.001 to 0.1 normal in the presence of a contact mass comprising iron fragments having a size of about one-fourth inch to one inch.

4. The process of removing small amounts of oxygen from a hydrocarbon fluid containing also hydrogen sulfide which comprises contacting said fluid in the presence of metallic iron with a dilute acidic aqueous solution having a hydrogen ion concentration not greater than about 0.1 normal but sufiicient to prevent precipitation of iron sulfide.

5. The process of removing small amounts of oxygen from a hydrocarbon fluid containing the same, comprising continuously passing said fluid upwardly through a vessel containing a contact mass comprising iron fragments, simultaneously passing a dilute acidic aqueous solution having a hydrogen ion concentration of about 0.01 to 0.1 normal downwardly through said vessel, withdrawing said solution from the lower portion of said vessel and returning the same to the upper portion of said vessel.

6. The process of removing small amounts of oxygen from a hydrocarbon fluid containing the same, comprising continuously passing said fluid upwardly through a vessel containing a contact mass comprising iron fragments, simultaneously passing a dilute acidic aqueous solution having a hydrogen ion concentration of about 0.001 to 0.1 normal downwardly through said vessel, withdrawing said solution from the lower portion of said vessel, settling said withdrawn solution to remove solids therefrom and introducing the resulting clear solution into the upper portion of said vessel.

WILLIAM B. PLUMMER. MAURICE H. ARVESON. 

